Improvement in propellers for vessels



T. M. RANKIN.

PROPELLERSFOR vEssELsf Tate'nted Marc-1114,1876.

II Illlllllllllllll Ilium N-PETERS. PNOTO-LITEOGRAPHEE WBSIiINGTO D. C.

nirnn STATES PATENT OFFIO IMPROVEMENT IN PROPELLERS FOR VESSELS.

Specification forming part of Letters Patent No. 174,854, dated March 14, 1876 application filed April 5, 1875. I

To all whom it may concern Be it known that I, THOMAS M. RANKIN, of Modesto, in the county of Stanislaus and State of California, have invented a new and useful Propeller or Motor for Vessels, of which the following is a specification: v

The object of my invention is the produc tion of a substitute for the screw-propeller which will reduce the jar or vibration of the hull, caused by the blades of the screw acting improperly upon the water, and remove the liability of breaking either of the blades.

The construction of my propeller is illustrated by Figure 1 of the drawing, and its application to a vessel .by Fig. 2. In Fig. 3 is shown a view of the propeller from behind, and in Figs. 4 and 5 its position in the water at different points of revolution of the shaft. Fig. 6 illustrates the action of the blades as the pressure upon one or the other varies.

Figs. 7,8, and 9, show different forms of blades.

The propeller consists essentially of two blades, A A, fixed upon a shaft, a, at an angle with each other, and connected with and secured to the driving-shaft of thevengin'e or other motive power. The blades A A are made of thin metal, of astrength and thickness proportionate to the size of propeller, either in one piece or of several sheets of metal, riveted together and strengthened by means of ribs and flanges to hold them in shape against the action of the water. They are secured to the shaft at either in a fixed manner or by devices that will permit them to be adjusted and held at any angle with each other.

In the figures of the drawing, the blade A is fixed to the shaft or, while the other, A, is adjustable around it, and thus, in adjusting the propeller to the vessel and to the work required from it, the angle between the faces of the blades can be changed as desired; but the set-screw shown in this case to hold the blade A upon the shaft would not answer in applying the propeller in a practical manner, and other and stronger means, therefore, would be necessary to hold the blade properly in position; or, in cases where the proper pitch or angle of the blades is established, the adjustment before mentioned may be dispensed with, and the two blades may be secured rigidly to their shaft. The shaft 00 passes through the collar 12 or enlarged portion of the driving-shaft B, and is held always perpendicularly to the driving-shaft, but yet with sufficient play to permit the shaft a to turn, or rotate, in it; so that,-although the motion of the blades around the driving-shaft is always positive, and in a circle, of which the shaft and collar is the center, yet the blades and their shaft or are free to turn, as the water in which they are immersed acts upon their surfacewith different degrees and changes of pressure.

From this manner of constructing and arranging the propeller, it will be seen, by

reference to Fig. 1 of the drawing, that as the driving-shaft B is revolved in the direction of the arrow, the under surface of the blade A is pressed down upon the body of water beneath it, and, by virtue of its angular position in the water, it must act to move the shaft B, and the vessel in which it is moved, in the direction indicated by the straight arrow; and further, it will be seen that, while the blade A is pressing down upon the water beneath it, the other blade A--is acting in a sim-] ilar manner upon the body of water above and in contact with its upper surface. Under these conditions the tendency of each of the blades, when in the position shownin Fig. 1, is to take a perpendicular position, or the one offering the least resistance; but, as they are I fixed upon the shaft a, the pressure upon one blade holds the other against the pressure of the water; thus the equilibrium is preserved and the pressure equalized between them as they revolve.

To illustrate this, let the broken line 0 represent one element in the pressure upon the blade A, and the corresponding line 0 an element in the pressure upon the blade A. So

it and forcing its way below the surface by displacement.

This action may be illustrated by Figs. 4, 5, and 6 of the drawing, where W L may represent the water-line, or surface of the water in which the propeller is working, and the arrows may show both the direction of the motion of the driving-shaft and the travel of the vessel. If, therefore, at any time the blades are thrown above the surface WV L, Fig. 4, the continued revolution of the driving-shaft will cause the blade so exposed to enter the water in the positions shown in Figs. 5 and 6, thus causing it to cut edgewise into and be low the water.

In the points of defective action and liability to bebroken, found in the propellers now in use, my invention is a greatimprovement, and the mode of acting upon the water, already described, renders its operation smoothan regular.

No excessive strain is thrown upon one portion at any time at the expense of the other part, as the acting-surface of the blades is as broad at the part near the driving-shaft as at the other end so this part that is the weakest point in the screw-propeller can be strengthened without decreasing the force of the propeller by adding to it such matter that will only tend to increase its weight without giving it greater actingsurface. And, further, as its operation when immersed is similar to the action of natural motors, as illustrated in the movements of a fish, no cutting up or thrashing of the water is produced, but a regular pressing and pushing movement is done by the blades with but a small amount of disturbance of the water, and consequently no power is thrown away.

In the several views of the drawing, the

blades A A are shown as set at an angle of a little less than ninety degrees to each other; but this may be changed, as Ido notconfine my construction to any particular angle, though I prefer to set themat about right angles. But this may depend upon the conditions attending the application of my propeller to difi'erent kinds of vessels, and the power required from it, for, in employing a propeller of this kind to drive canal or other boats traveling in shallow water, I should make the blades longer and narrower in proportion to'those shown in Figs. 1, 2, 3, and 4, so that they would have afor'm something like those shown in Figs. 8 and9, and in such cases it might be necessary to make the angle less, as otherwise they would have too wide a sweep. It might also be desirable in these cases to make the ends of the blades of curved form, or of the shape shown in Figs. 7 and 8 but these are modifications in the construction of this propeller that are not essential to the principle of its operation, and do not change the character of my invention.

It will be seen, by referring to Figs. 1 and 2 of the drawing, that, as the motion of the driving-shaft B is reversed, the blades A A turn over and take hold of the water in a position opposite to that taken by them before the shaftin Fig. 2, being rotated in the direction of the curved arrow, produces a motion of the vessel 0 in the direction indicated by the straight arrow, while' its rotation in the A propeller for vessels, having the following elements, viz: a driving-shaft, a cross-shaft passing at right angles through said drivingshat't, and capable of rotary motion therein, and blades attached to said cross-shaft, substantially as and for the purposes set forth.

'rnos. M. RANKIN.

Witnesses:

(J. W. M. SMITH, EDWARD OSBOBN. 

